Covalent Drug Binding in Live Cells Monitored by Mid-IR Quantum Cascade Laser Spectroscopy: Photoactive Yellow...

Area of Science:

• Biochemistry
• Spectroscopy
• Molecular Biology

Background:

• Live-cell detection of drug-target interactions is crucial for understanding therapeutic compound behavior.
• Genetically encoded nitrile probes offer sensitive reporting of molecular interactions.
• Low signal-to-noise ratios have limited nitrile probe utility in live cells.

Purpose of the Study:

• To design a highly sensitive spectrometer for detecting nitrile vibrational probes in live cells.
• To investigate small-molecule binding to proteins within a cellular environment.
• To model covalent drug binding using a para-coumaric acid and nitrile-incorporated photoactive yellow protein system in E. coli.

Main Methods:

• Development of a double-beam quantum cascade laser (QCL)-based transmission infrared (IR) spectrometer with balanced detection.
• Utilizing nitrile vibrational probes embedded in proteins within E. coli.
• Employing molecular dynamics simulations with the AMOEBA force field.

Main Results:

• The QCL spectrometer significantly enhanced sensitivity for nitrile probes compared to FTIR.
• Detected small-molecule binding, specifically para-coumaric acid to nitrile-PYP, within live E. coli.
• Observed large spectral shifts (up to 15 cm⁻¹) in bound vs. unbound states, attributed to altered hydrogen-bonding environments.

Conclusions:

• The QCL spectrometer provides enhanced sensitivity for monitoring drug-protein interactions in live cells.
• This technology offers a powerful model for investigating drug binding and covalent interactions in cellular systems.
• Findings pave the way for advanced drug development and biochemical research methodologies.